for National Geographic News
The United States averages just 16 shark attacks each year and slightly less than one shark-attack fatality every two years. Meanwhile, in the coastal U.S. states alone, lightning strikes and kills more than 41 people each year.
Which just goes to show that sharks enjoy a reputation that is arguably more fearsome than their bite. Read on for more surprising shark facts compiled by National Geographic News:
Each year there are about 50 to 70 confirmed shark attacks and 5 to 15 shark-attack fatalities around the world. The numbers have risen over the past several decades but not because sharks are more aggressive: Humans have simply taken to coastal waters in increasing numbers.
Over 375 shark species have been identified, but only about a dozen are considered particularly dangerous. Three species are responsible for most human attacks: great white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and bull (Carcharhinus leucas) sharks.
While sharks kill fewer than 20 people a year, their own numbers suffer greatly at human hands. Between 20 and 100 million sharks die each year due to fishing activity, according to data from the Florida Museum of Natural History's International Shark Attack File. The organization estimates that some shark populations have plummeted 30 to 50 percent.
The shortfin mako (Isurus oxyrinchus) is often recognized as the world's speediest shark. It has been clocked at speeds of up to 20 miles an hour (32 kilometers an hour) and can probably swim even faster than that. Makos are fast enough to catch even the fleetest fish, such as tuna and swordfish.
The largest shark is the whale shark (Rhincodon typus), which can grow to 60 feet (20 meters) long. The gentle giant eats tiny plankton.
Among the smallest shark species is the deepwater dogfish shark (Etmopterus perryi). A habitué of the Caribbean, the dogfish measures a less-than-intimidating 8 inches (20 centimeters) in length.
Sharks are known as eating machines. But because many species are cold-blooded, some sharks eat only about 2 percent of their body weight each day. That's a bit less than humans typically eat.
While scientists still have much to learn about shark migration, researchers do know that some species get around. Blue sharks (Prionace glauca), for example, roam the North Atlantic on journeys of 1,200 to 1,700 nautical miles (2,220 to 3,145 kilometers). After one record-breaking blue was tagged off New York, it swam 3,740 nautical miles (6,919 kilometers) to Brazil.
Some sharks must swim constantly to "breathe" oxygen from water passing through their gills. Other species can achieve this while stationary.
Sharks do not sleep. Rather, they experience alternating periods of activity and rest.
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